MAJOR GOALS are to study the roles of the cerebellum and basal ganglia in adapting, learning and storing adjustments of eye-hand coordination. Gaze will be perturbed with laterally displacing prisms (project #1) and with shift of the visual target (project #2 ) to see how monkeys adjust their reaching to visual targets. Two types of adjustment are distinguished, leaming and adaptation. In leaning, a monkey stores two gaze-reach calibrations, and can call each up immediately if it knows each condition. In adaptation, there is only one stored gaze-reach calibration, which must be adjusted back and forth by practice. Project # 1 examines whether the cerebellum and basal ganglia are both necessary for storing learned gaze-reach calibrations. Monkeys will have two gaze-reach calibrations: 1) reaching to and touching a visual target without prisms, in which eyes and reach are aligned, and 2) learned reaching to and touching a visual target with prisms, in which eyes and reach are divergent. Neurons in cerebellar cortex, deep nuclei, and globus pallidus pars interna will be recorded from then inactivated to see if the learned gaze-reach adjustment is abolished. Project # 2 asks how the cerebellar cortex, inferior olive, and parvocellular red nucleus are involved in adapting and learning to touch a visual target that has shifted in mid-reach. At the start of each block of adaptation shift trials, the visual target will shift mid-reach in a novel direction, and continue each trial to shift in that direction for the rest of the block. The monkey must adapt in order to touch the target at its shifted novel location. Then the monkey will have a block of no-shift trials, and must then dis-adapt in order to hit the target where it initially appears. During learning shift trials, the target will shift in a direction that is fixed and therefore predictable throughout the block and all such blocks of trials. The monkey will be informed that this is the learned shift condition and thus can learn it, in addition to the no-shift condition. This project focuses on the problem of how subjects adapt and learn when knowledge of results is delayed after the movement. Recording Purkinje cell firing and recording from and inactivating neurons of the parvocellular red nucleus will help to understand their involvement.